1. Field of the Invention
This invention relates to an apparatus and method for electrically testing multi-core cables and more particularly it relates to testing the conductive state of each of the cores of a multi-core cable, such as a communication cable, having a number of cores, each comprising a conductor and an insulating cover.
2. Description of the Prior Art
Usually, a communication cable is constructed using as a structural unit a pair in which two cores are twisted together or a quad in which four cores are twisted together. Some local communication cables containing a number of cable circuits comprise as many as 2,400 to 3,200 pairs, i.e., 4,800 to 6,400 cores may be contained in a single cable. In the production of such communication cables, the cores have to be tested one by one in the intermediate or final stage of cable production to see if there is a break in any of the conductors, in order to guarantee the quality of each cable. Further, in order to carry out such tests, all the cores have to be stripped of their insulating covers at both ends of the cable.
However, it would require an enormous amount of time and labor to test the cores by successively selecting and separating a single core from a large group of cores as described above. Therefore, various attempts to mechanically or automatically carry out such discontinuity tests of multi-core cables (including other electrical tests) have heretofore been suggested and realized.
For example, there has been developed an apparatus comprising a measuring multi-pole connector or multi-pole insulated terminal stand having terminals to which the cores of a cable are once connected, whereupon the cores are successively automatically tested for their breaks or continuity by a measuring instrument, through said connector or terminal stand. However, carrying out tests by using such an apparatuses takes much time for preparation, connection and disconnection upon completion of the test. Hence, prior art devices fail to provide an efficient automatic testing. That is, the preparatory operation for removing the insulating covers from the cores or untwisting the cores and straightening them in order to connect the cores to the terminals on said connector, the operation for picking up the cores one by one for connection to the terminals or the after-operation for disconnecting the tested cores without damaging them cannot be performed except manually. As a result, these operations require a long time and the ratio which the net time required for inspection and measurement bears to the whole time is small. Thus, even if the measuring operation alone is automated, it would be impossible to improve the efficiency of operation drastically, since the picking and connecting operations which occupy the greater part of the process are not automatic.